Energy storage system, transportation unit, and method of controlling energy storage system

ABSTRACT

An energy storage system includes an energy storage provided in a transportation unit, a connector electrically connectable to an external power transmission management apparatus, a power transmission circuit, and a processor. The processor is configured to control the power transmission circuit in accordance with an output from the external power transmission management apparatus to perform power transmission between the energy storage and an external power system, and control the power transmission circuit in accordance with an output from the external power transmission management apparatus, if a degree of variation in charging states in the energy storage and one or more external energy storages is greater than or equal to a threshold value, to perform power transmission between the energy storage and the one or more external energy storages to reduce the degree of variation before performing the power transmission between the energy storage and the external power system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2016-234692, filed Dec. 2, 2016,entitled “Energy Storage System, Transportation Unit, and Method ofControlling The Energy Storage System.” The contents of this applicationare incorporated herein by reference in their entirety.

BACKGROUND 1. Field

The present disclosure relates to an energy storage system, atransportation unit, and a method of controlling an energy storagesystem.

2. Description of the Related Art

For instance, as described in Japanese Patent No. 5440158, a techniquehas been proposed which charges an energy storage having a small amountof stored energy by transmitting power from a vehicle including anenergy storage having a large amount of stored energy to a vehicleincluding the energy storage having a small amount of stored energy outof multiple vehicles in order to avoid a situation (eventually, toprotect against acceleration of deterioration of the energy storages) inwhich respective energy storages of the multiple vehicles are left in astate where the amounts of stored energy of the energy storages areexcessively low or excessively high for a long time.

SUMMARY

According to one aspect of the present invention, an energy storagesystem of the present disclosure includes: an energy storage mounted ina transportation unit; a connector that is electrically connectable toan external power transmission management apparatus, and that, in aconnected state, allows power transmission, via the power transmissionmanagement apparatus, between an external power system electricallyconnected to the power transmission management apparatus, and one ormore external energy storages electrically connected to the powertransmission management apparatus; a power transmission circuitinterposed between the connector and the energy storage; a controllerthat has a function of controlling the power transmission circuit. Thecontroller has a function that, in a state where the connector iselectrically connected to the power transmission management apparatus,performs A control processing to control the power transmission circuitin accordance with a command issued from the power transmissionmanagement apparatus so that power transmission is performed between theenergy storage and the power system, and a function that, when a degreeof variation in states of charge of a plurality of energy storagesincluding the energy storage and the one or more external energystorages is greater than or equal to a predetermined threshold value,performs B control processing to control the power transmission circuitbefore the A control processing is performed to reduce the degree ofvariation, in accordance with a command issued from the powertransmission management apparatus so that power transmission isperformed between the energy storage and the one or more external energystorages via the power transmission management apparatus (a first aspectof the disclosure).

According to another aspect of the present invention, a method ofcontrolling an energy storage system in the present disclosureincluding: an energy storage mounted in a transportation unit, aconnector that is electrically connectable to an external powertransmission management apparatus, and that, in a connected state,allows power transmission, via the power transmission managementapparatus, between an external power system electrically connected tothe power transmission management apparatus, and one or more externalenergy storages electrically connected to the power transmissionmanagement apparatus, and a power transmission circuit interposedbetween the connector and the energy storage, the method including: in astate where the connector is electrically connected to the powertransmission management apparatus, controlling the power transmissioncircuit to perform power transmission between the energy storage and thepower system, and when a degree of variation in states of charge of aplurality of energy storages including the energy storage and the one ormore external energy storages is greater than or equal to apredetermined threshold value, to reduce the degree of variation beforethe controlling the power transmission circuit, controlling the powertransmission circuit to perform power transmission between the energystorage and the one or more external energy storages via the powertransmission management apparatus (12th aspect of the disclosure).

According to further aspect of the present invention, an energy storagesystem includes an energy storage provided in a transportation unit, aconnector electrically connectable to an external power transmissionmanagement apparatus that is electrically connectable to an externalpower system and one or more external energy storages, a powertransmission circuit interposed between the connector and the energystorage, and a processor. The processor is configured to control thepower transmission circuit in accordance with an output from theexternal power transmission management apparatus to perform powertransmission between the energy storage and the external power system,and control the power transmission circuit in accordance with an outputfrom the external power transmission management apparatus, if a degreeof variation in charging states in the energy storage and the one ormore external energy storages is greater than or equal to a thresholdvalue, to perform power transmission between the energy storage and theone or more external energy storages via the external power transmissionmanagement apparatus to reduce the degree of variation before performingthe power transmission between the energy storage and the external powersystem.

According to further aspect of the present invention, a method ofcontrolling an energy storage system is disclosed. The method includescontrolling a power transmission circuit to perform power transmissionbetween an energy storage and an external power system, the energystorage system including the energy storage provided in a transportationunit, the connector electrically connectable to the external powertransmission management apparatus that is electrically connectable tothe external power system and one or more external energy storages, andthe power transmission circuit interposed between the connector and theenergy storage, and if a degree of variation in states of charge of theenergy storage and the one or more external energy storages is greaterthan or equal to a threshold value, controlling the power transmissioncircuit to perform power transmission between the energy storage and theone or more external energy storages via the power transmissionmanagement apparatus to reduce the degree of variation before performingthe power transmission between the energy storage and the external powersystem.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

FIG. 1 a diagram illustrating the entire configuration of a systemincluding a vehicle (transportation unit) equipped with a power storagesystem in an embodiment of the present disclosure.

FIG. 2 is a block diagram illustrating the configuration of powertransmission between a power transmission management apparatus and avehicle.

FIGS. 3A and 3B are graphs for explaining the power transmission betweena power transmission management apparatus and a power system.

FIG. 4 is a flowchart illustrating the control processing (SOC variationreduction processing) of a power transmission management apparatus and avehicle.

FIG. 5 is a flowchart illustrating the control processing (SOC variationreduction processing) of a power transmission management apparatus and avehicle.

FIG. 6 is a diagram illustrating a change in the state of charge of theenergy storages of multiple vehicles caused by the SOC variationreduction processing.

FIG. 7 is an explanatory diagram of incentive obtained by the users ofvehicles in the embodiment.

FIG. 8 is an explanatory diagram of incentive obtained by the users ofvehicles in a comparative example.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

An embodiment of the present disclosure will be described below withreference to FIGS. 1 to 8. Referring to FIG. 1, the entire systemdescribed in this embodiment is an example of so-called a vehicle togrid (V2G) system, and includes power transmission management apparatus1, multiple vehicles 10, 10, . . . as transportation units, a powergeneration facility 20, and a power system 30.

The power generation facilities 20 is formed by facility of wind powergeneration, solar power generation, thermal power generation, andnuclear power generation, for instance. The power generation facilities20 is electrically connected to a connector 1 c of the powertransmission management apparatus 1 so that power can be supplied to thepower transmission management apparatus 1.

It is to be noted that “an any object A (or facility A) is “electricallyconnected” to another object B (or facility B)” in description of thisembodiment indicates a state where power can be transmitted between Aand B at any time (an electric line between A and B is formed). In thiscase, “electrical connection” between A and B is not limited to aconnection state due to contact between conductors, and may be aconnection state where power transmission between A and B is performedwirelessly (via electromagnetic wave energy).

The power system 30 is a facility (transmission network) that suppliespower to power receiving facilities 31, 31, . . . of multiple powerconsumers. The power system 30 is electrically connected to a connector1 a of the power transmission management apparatus 1 so that power canbe transmitted between the power transmission management apparatus 1 andthe power system 30.

As illustrated in FIG. 2, each vehicle 10 is a vehicle (for instance, anelectric vehicle or a hybrid vehicle) that is equipped with an energystorage 12 having a relatively high capacity. The energy storage 12 isformed as an aggregate of multiple cells including a secondary batterysuch as a lithium ion battery, or a capacitor, for instance.

Each vehicle 10 is pre-registered in the power transmission managementapparatus 1 as a vehicle that is capable of transmitting power (chargepower or discharge power of the energy storage 12) between the energystorage 12 and the power transmission management apparatus 1.

It is to be noted that in this embodiment, the energy storage 12 of anyone vehicle 10 of the multiple vehicles 10 corresponds to the energystorage (mounted energy storage) mounted in the transportation unit inthe present disclosure, and the energy storage 12 of another vehicle 10corresponds to the external energy storage in the present disclosure.

The energy storage 12 of each vehicle 10 is electrically connected to anexternal charging apparatus 5 installed in a parking lot of the vehicle10, and thus the energy storage 12 is electrically connected to aconnector 1 b of the power transmission management apparatus 1 via theexternal charging apparatus 5.

More particularly, each vehicle 10 is equipped with a power storagesystem 11 including equipment for performing power transmission betweenthe energy storage 12 and the external charging apparatus 5. In additionto the energy storage 12, the power storage system 11 includes aconnector 13 that is electrically connectable to the external chargingapparatus 5, an AC-DC converter 14 serving as a power transmissionequipment that performs power transmission between the energy storage 12and the connector 13, a controller 15 that controls power transmissionbetween the external charging apparatus 5 and the energy storage 12 viathe AC-DC converter 14, a controller 16 that performs control processingrelated to monitoring and management of the state of the energy storage12, and a power line communication (PLC) unit 17 for power linecommunication between the external charging apparatus 5 and the vehicle10. It is to be noted that the connector 13 corresponds to the connectorin the present disclosure, the AC-DC converter 14 corresponds to thepower transmission circuit in the present disclosure, and the controller15 corresponds to the controller in the present disclosure.

Here, the external charging apparatus 5 is a terminal that relays powertransmission between the power transmission management apparatus 1 andthe vehicle 10 in a state electrically connected to the connector 13 ofthe vehicle 10. The external charging apparatus 5 is electricallyconnected to the connector 1 b of the power transmission managementapparatus 1 so that power can be transmitted between the powertransmission management apparatus 1 and the external charging apparatus5.

In a state where the external charging apparatus 5 is electricallyconnected to the connector 13 of the vehicle 10, the external chargingapparatus 5 can receive the power to be charged to the energy storage 12of the vehicle 10 from the power transmission management apparatus 1, orcan receive discharge power of the energy storage 12 from the vehicle10, and can transmit the power to the power transmission managementapparatus 1. Therefore, the external charging apparatus 5 iselectrically connected to the connector 13, and consequently the energystorage 12 of each vehicle 10 is electrically connected to the connector1 b of the power transmission management apparatus 1 via the externalcharging apparatus 5.

It is to be noted that in this embodiment, the power transmitted betweenthe external charging apparatus 5 and the vehicle 10 is the AC power.

Also, the external charging apparatus 5 is equipped with a PLC unit 5 athat performs power line communication between the PLC units 17 of thevehicle 10. The PLC unit 5 a can communicate with the later-describedcontroller 3 of the power transmission management apparatus 1 via acommunication network such as the Internet. Consequently, communicationis possible between the vehicle 10 and the power transmission managementapparatus 1 via the PLC units 5 a, 17.

The AC-DC converter 14 is an electronic device that is capable ofconverting power from one of AC power and DC power to the other by thecontrol by the controller 15. The power storage system 11 is controlledso that when power is transmitted from the external charging apparatus 5to the energy storage 12 (when the energy storage 12 is charged), theAC-DC converter 14 converts AC power inputted from the external chargingapparatus 5 via the connector 13 to DC power, and supplies the DC powerto the energy storage 12.

The power storage system 11 is controlled so that when power istransmitted from the energy storage 12 to the external chargingapparatus 5 (when the energy storage 12 is discharged), the AC-DCconverter 14 converts DC power inputted from the energy storage 12 to ACpower, and supplies the AC power to the external charging apparatus 5.

It is to be noted that the AC-DC converter 14 is configured to variablycontrol the amount of transmission of power between the externalcharging apparatus 5 and the energy storage 12.

The controllers 15, 16 are formed of one or multiple electronic circuitunits including a CPU, a RAM, a ROM, an interface circuit. As thefunctions achieved by implemented hardware configuration or programs(software configuration), the controller 15 has a function ofcontrolling the AC-DC converter 14, a function of communicating with theexternal charging apparatus 5 or the power transmission managementapparatus 1 via the PLC unit 17, and a function of communicating withthe controller 16.

In this case, the controller 15 can obtain data such as a state ofcharge (SOC), a temperature of the energy storage 12, indicating a stateof the energy storage 12 by the communication with the controller 16.

Furthermore, the controller 15 can receive a command related todischarge or charge of the energy storage 12 by the communication withthe external charging apparatus 5 from the power transmission managementapparatus 1 via the external charging apparatus 5, or can transmit thedata indicating the state of charge (hereinafter referred to as the SOC)of the energy storage 12 to the power transmission management apparatus1 via the external charging apparatus 5.

The controller 16 receives input of detection data indicating thevoltage, current, and temperature of the energy storage 12 from a sensorwhich is not illustrated. As the functions achieved by implementedhardware configuration or programs (software configuration), thecontroller 16 has a function of sequentially estimating an SOC of theenergy storage 12 based on the inputted detection data, and a functionof communicating with the controller 15.

As a supplement, communication between the external charging apparatus 5and the vehicle 10 may be performed by a communication system other thanPLC (for instance, wireless communication such as Wi-Fi (registeredtrademark) or Bluetooth (registered trademark), or a wired communicationusing a signal line for communication).

Also, the controller 15 of the vehicle 10 may be configured to directlycommunicate with the power transmission management apparatus 1 via acommunication networks such as the Internet. Also, the controllers 15,16 of the vehicle 10 may be collectively formed as a single electroniccircuit unit.

Also, the external charging apparatus 5 and the power storage system 11may be configured to perform power transmission between the externalcharging apparatus 5 and the vehicle 10 by DC power. In this case, thepower storage system 11 may include, for instance, a DC-DC converter asa power transmission equipment that works between the energy storage 12and the connector 13.

As illustrated in FIG. 1, the power transmission management apparatus 1includes a power transmission equipment 2 that transmits power betweenthe connectors 1 a, 1 b, 1 c, and the power transmission equipment 2,and a controller 3 that controls the power transmission equipment 2.

The power transmission equipment 2 includes, for instance, multipleswitches and electrical relays. Also, the controller 3 is formed of oneor more electronic circuit units including a CPU, a RAM, a ROM, aninterface circuit, or one or more computers, or a combination of theseelectronic circuit units and computers. It is to be noted that thecomponents of each of the power transmission equipment 2 and thecontroller 3 may be distributed over multiple portions.

The controller 3 has a function of controlling the power transmissionequipment 2 by implemented hardware configuration or programs (softwareconfiguration). In this case, the controller 3 is capable of controllingon/off of an electric line for performing power transmission between theconnectors 1 a, 1 b, and 1 c, and of controlling on/off of an electricline for performing power transmission between the energy storages 12 ofmultiple vehicles 10 electrically connected to the connector 1 b.

The power transmission management apparatus 1 is capable of transmittingpower from the connector 1 b or 1 c to the connector 1 a so that thepower received from the energy storage 12 of each vehicle 10 or thepower generation facilities 20 is supplied to the power system 30 bycontrolling the power transmission equipment 2 using the controller 3 asappropriate, or of transmitting the power received from the powergeneration facilities 20 or the power system 30 to the energy storage 12of each vehicle 10 from the connector 1 a or 1 c via the connector 1 bso that the energy storage 12 of each vehicle 10 is charged, or oftransmitting power between the respective energy storages 12 of multiplevehicles 10, 10, . . . (in other words, supplying the power receivedfrom the energy storage 12 of one vehicle 10 to the energy storage 12 ofanother vehicle 10).

In this case, power transmission between the power transmissionmanagement apparatus 1 and the power system 30 is performed inaccordance with the contract made between a business operator of thepower transmission management apparatus 1 and a business operator of thepower system 30.

For instance, as illustrated by the graph of FIG. 3A, in a time periodTW (contracted time period) in which the power load of the power system30 is predicted to increase rapidly during a day, power having apredetermined amount of power, contracted as so-called an instantaneousreserve power is supplied from the power transmission managementapparatus 1 to the power system 30.

It is to be noted that more particularly, “electric power load” for thevertical axis in the graph of FIG. 3A is the amount of power obtained bysubtracting the entire amount of power supplied to the power system 30for regular use from the entire requested amount of power to the powersystem 30.

Hereinafter, supplying power as an instantaneous reserve power from thepower transmission management apparatus 1 to the power system 30 asdescribed above is referred to as instantaneous reserved powertransmission processing. In the instantaneous reserved powertransmission processing, the power transmission management apparatus 1basically transmits the total amount of power received from therespective energy storages 12 of the multiple vehicles 10, 10, . . . tothe power system 30. In this case, the amount of power to be transmittedto the power system 30 and an execution time period for theinstantaneous reserved power transmission processing are contracted.

Also, as illustrated by a dashed line portion of the graph of FIG. 3B,in a situation in which the waveform of power supplied to each powerreceiving facility 31 by the power system 30 includes a fluctuationcomponent with a frequency higher than a reference frequency, powertransmission from the power transmission management apparatus 1 to thepower system 30, and power transmission from the power system 30 to thepower transmission management apparatus 1 are alternately repeated in arelatively short period so that the fluctuation component is reduced(eventually, distortion of the power waveform is reduced).

Hereinafter, giving and receiving power between the power transmissionmanagement apparatus 1 and the power system 30 as described above isreferred to as frequency adjustment processing. In the frequencyadjustment processing, the power transmission management apparatus 1basically transmits the total amount of power received from therespective energy storages 12 of the multiple vehicles 10, 10, . . . tothe power system 30 at the time of power transmission to the powersystem 30, and distributes and supplies received power to the respectiveenergy storages 12 of the multiple vehicles 10, 10, . . . at the time ofpower reception from the power system 30. Therefore, in the frequencyadjustment processing, charge and discharge of the respective energystorages 12 of the multiple vehicles 10, 10, . . . are periodicallyrepeated. In this case, the amount of transmission of power (the amountof transmitted power and the amount of received power) per periodbetween the power transmission management apparatus 1 and the powersystem 30, and an execution time period for the frequency adjustmentprocessing are contracted.

It is to be noted that the above-mentioned contract information (theamount of electricity transmitted and the execution time period in theinstantaneous reserved power transmission processing, and the amount oftransmission of power per period and the execution time period in thefrequency adjustment processing) on the instantaneous reserved powertransmission processing and the frequency adjustment processing isinputted to the controller 3 via an input device (not illustrated) orfrom another computer, and is recorded and held.

Also, the controller 3 of the power transmission management apparatus 1includes a recorder 3 a (database) that records each pre-registeredvehicle 10 as the vehicle 10 that can perform power transmission betweenthe power transmission management apparatus 1 and the vehicle 10, andinformation (hereinafter simply referred to as vehicle-to-vehicleinformation) on the user of each vehicle 10. The vehicle-to-vehicleinformation includes for instance, information (such as a mail address)indicating a destination of transmission of various data to each vehicle10 or a user, information on incentive to the user of each vehicle 10,information indicating payment cost (bearing cost) to the user of eachvehicle 10, and history information on power transmission between eachvehicle 10 and the power transmission management apparatus 1.

Here, in this embodiment, when power transmission is performed betweenthe energy storage 12 of each vehicle 10 and the power transmissionmanagement apparatus 1 by the instantaneous reserved power transmissionprocessing or the frequency adjustment processing, incentive such asmoney or points is given to the user of the vehicle 10 by a businessoperator of the power transmission management apparatus 1 for eachprocessing.

Also, in this embodiment, power is transmitted (given and received)between the respective energy storages 12 of the multiple vehicles 10,10, . . . by the later-described SOC variation reduction processing. Inthis case, an incentive (positive incentive) is given to the user of avehicle 10, who has discharged the energy storage 12, whereas bearing ofcost (negative incentive) is imposed on the user of a vehicle 10, whohas charged the energy storage 12.

The above-mentioned incentive information recorded on the recorder 3 aincludes, for instance, information indicating the value of incentive(cumulative incentive value) acquired by the user of each vehicle 10,and information indicating an acquisition history and a usage history ofincentive. It is to be noted that when the user of each vehicle 10consumes an incentive as needed, the cumulative incentive value of theuser is decreased by an amount corresponding to the consumption.

Also, when the user charges the energy storage 12 of each vehicle 10 upto a desired amount, the payment cost is the cost to be paid by a useraccording to the amount of charge.

The controller 3 can transmit the above-mentioned incentive informationon the payment cost to each vehicle 10 as needed, or to a terminal suchas a smartphone, a tablet terminal, and a personal computer used by theuser of each vehicle 10.

As a supplement, the energy storages 12 of multiple vehicles 10 andanother power supply source (for instance, a stationary large-capacityenergy storage) different from the power generation facilities 20 may beelectrically connected to the power transmission management apparatus 1.

Next, the operation (particularly, the operation related to the powertransmission of the power transmission management apparatus 1 and theenergy storage 12 of each vehicle 10) of the system in this embodimentwill be described below.

When the user of each vehicle 10 parks the vehicle 10 in a parking lotin which the external charging apparatus 5 is utilizable, the externalcharging apparatus 5 is electrically connected to the connector 13 ofthe vehicle 10 by the user. Thus, the energy storage 12 of the vehicle10 is electrically connected to the connector 1 b of the powertransmission management apparatus 1 via the external charging apparatus5.

In a time period before power transmission between the powertransmission management apparatus 1 and the power system 30 is performedby the instantaneous reserved power transmission processing or thefrequency adjustment processing, the controller 3 of the powertransmission management apparatus 1 performs control processing(hereinafter referred to as SOC variation reduction processing), incooperation with the controller 15 of each vehicle 10, for reducing avariation in the SOC, as much as possible, of the respective energystorages 12 of the multiple vehicles 10, 10, . . . electricallyconnected to the connector 1 b via the external charging apparatus 5. Itis to be noted that the processing performed by the controller 15 ofeach vehicle 10 out of the SOC variation reduction processingcorresponds to the B control processing in the present disclosure.

In this case, when starting the SOC variation reduction processing, forall the vehicles 10 electrically connected to the power transmissionmanagement apparatus 1, the controller 3 of the power transmissionmanagement apparatus 1 transmits data indicating start of execution ofthe SOC variation reduction processing to the PLC unit 17 of eachvehicle 10 via the PLC unit 5 a of the external charging apparatus 5electrically connected to the connector 13 of each vehicle 10.

At this point, the PLC unit 17 of each vehicle 10 which has received thedata activates the controllers 15, 16 of the vehicle 10. Morespecifically, the PLC unit 17 of each vehicle 10 supplies power sourceto the controller 15, 16, for instance, by controlling the power sourcecircuit (not illustrated) of the controllers 15, 16 of the vehicle 10.Thus, the controllers 15, 16 are activated.

After the controllers 15, 16 of each vehicle 10 are activated in thismanner, the SOC variation reduction processing is performed asillustrated in the flowchart of FIGS. 4 and 5.

It is to be noted that in FIGS. 4 and 5, the processing (the processingin STEPS 1 to 13) in the center flowchart indicates the processingperformed by the controller 3 of the power transmission managementapparatus 1, the processing (the processing in STEPS 21 to 26) in theleft flowchart indicates the processing performed by the controller 15of the vehicle 10 equipped with the energy storage 12 that performsdischarge in the SOC variation reduction processing, and the processing(the processing in STEPS 31 to 36) in the right flowchart indicates theprocessing performed by the controller 15 of the vehicle 10 equippedwith the energy storage 12 that performs charge in the SOC variationreduction processing.

However, the processing in STEP 21, 31 and the processing in STEP 22, 32are performed by all the vehicles 10 electrically connected to the powertransmission management apparatus 1.

In STEP 21, 31, the controller 15 of each vehicle 10 transmits data,obtained from the controller 16 and indicating the current SOC(estimated value) of the energy storage 12, addressed to the powertransmission management apparatus 1 via the PLC unit 17. The data isreceived by the PLC unit 5 a of the external charging apparatus 5, thenis transmitted from the PLC unit 5 a to the controller 3 of the powertransmission management apparatus 1.

The transmission data is received by the controller 3 of the powertransmission management apparatus 1. Thus, the controller 3 obtains theSOC of the energy storage 12 of each vehicle 10 (STEP 1).

In STEP 22, 32, the controller 15 of each vehicle 10 transmits dataindicating a utilization plan of the vehicle 10 and data indicating arequest (charge/discharge request) for charge/discharge of the energystorage 12 to the power transmission management apparatus 1 via the PLCunit 17. These pieces of data are received by the PLC unit 5 a of theexternal charging apparatus 5, then is transmitted from the PLC unit 5 ato the controller 3 of the power transmission management apparatus 1.

The above-mentioned data indicating a utilization plan includes, forinstance, data indicating the next timing of start of use of the vehicle10 (or data indicating a non-use time period of the vehicle 10). Also,the above-mentioned data indicating a request for charge/dischargeincludes, for instance, data indicating whether or not charge/dischargeof the energy storage 12 by the instantaneous reserved powertransmission processing or the frequency adjustment processing ispermitted, and data indicating a target SOC (or a target value forincreased amount of SOC) of the energy storage 12 necessary until thevehicle 10 is used next time.

The utilization plan and the charge/discharge request are, for instance,the information set by operating a predetermined operation section ofthe vehicle 10 by the user of each vehicle 10 when the vehicle 10 isparked.

As a supplement, the external charging apparatus 5 may be configured sothat the utilization plan and the charge/discharge request are settable,for instance, by a predetermined operation of the external chargingapparatus 5, and data indicating the utilization plan and thecharge/discharge request may be transmitted from the external chargingapparatus 5 to the power transmission management apparatus 1.

Also, for instance, when a terminal such as a smartphone owned by theuser of each vehicle 10 is capable of communicating with the controller3 of the power transmission management apparatus 1, the data indicatingthe utilization plan and the charge/discharge request set by the usermay be transmitted from the terminal to the power transmissionmanagement apparatus 1 by the terminal.

The data indicating the utilization plan and the charge/dischargerequest of each vehicle 10 is received by the controller 3 of the powertransmission management apparatus 1. Thus, the controller 3 obtains theutilization plan and the charge/discharge request set for each vehicle10 (STEP 2).

Subsequently to obtaining the SOC of the energy storage 12 of eachvehicle 10 and the utilization plan and the charge/discharge request ofeach vehicle 10, in STEP 3, the controller 3 of the power transmissionmanagement apparatus 1 selects target vehicles for the SOC variationreduction processing (the vehicles 10 equipped with the energy storage12 that performs charge or discharge by the SOC variation reductionprocessing) from all the vehicles 10 electrically connected to the powertransmission management apparatus 1.

In STEP 3, target vehicles for the SOC variation reduction processingare selected from all the vehicles 10 electrically connected to thepower transmission management apparatus 1, the target vehiclesexcluding, for instance, the vehicle 10 for which it is specified by thecharge/discharge request that charge/discharge of the energy storage 12by the instantaneous reserved power transmission processing or thefrequency adjustment processing is not permitted, and the vehicle 10 inwhich the remaining time, specified by the utilization plan, until thenext timing of start of use of the vehicle 10 is relatively short, andit is predicted that the SOC variation reduction processing, theinstantaneous reserved power transmission processing, or the frequencyadjustment processing, or charge of the energy storage 12 up to a targetSOC specified by the charge/discharge request is not completed in theremaining time period.

The vehicles 10 selected in STEP 3 are each such a vehicle that providesthe power of the energy storage 12 to be utilized for power transmissionin the instantaneous reserved power transmission processing or thefrequency adjustment processing after execution of the SOC variationreduction processing, and hereinafter such a vehicle is referred to as apower utilization target vehicle 10.

Subsequently, in STEP 4, the controller 3 of the power transmissionmanagement apparatus 1 calculates an index value (hereinafter referredto as a SOC variation degree index value) indicating a degree ofvariation in the SOC (the SOC of each power utilization target vehicle10 obtained in STEP 1) of the energy storage 12 of each powerutilization target vehicle 10.

In this embodiment, for instance, a standard deviation of the SOC of theenergy storage 12 of each of the power utilization target vehicles 10 iscalculated as a SOC variation degree index value.

It is to be noted that as a SOC variation degree index value, forinstance, a variance may be calculated instead of the standarddeviation. Alternatively, for instance, the difference between a maximumand a minimum of the SOC of the energy storage 12 of each powerutilization target vehicle 10 may be calculated as the SOC variationdegree index value.

Subsequently, in STEP 5, the controller 3 of the power transmissionmanagement apparatus 1 determines whether or not the SOC variationdegree index value is greater than or equal to a predetermined thresholdvalue (whether or not the degree of variation in the SOC is high). Anegative result of the determination in STEP 5 reflects a situation inwhich the degree of variation in the current SOC of the energy storage12 of each power utilization target vehicle 10 is low (the SOCs of therespective energy storages 12 are the same or near values), or thedegree of variation is reduced by the processing in STEP 6 to 12described below. In this case, the controller 3 of the powertransmission management apparatus 1 completes the SOC variationreduction processing.

On the other hand, an affirmative result of the determination in STEP 5reflects a situation in which the degree of variation in the SOC ishigh. In this case, next, in STEP 6, in order to reduce the degree ofvariation in the SOC, the controller 3 of the power transmissionmanagement apparatus 1 selects discharge target vehicles 10 in which theenergy storage 12 is to be discharged, and charge target vehicles 10 inwhich the energy storage 12 is to be charged, from the power utilizationtarget vehicles 10 in accordance with a predetermined rule.

In STEP 6, for instance, out of all the power utilization targetvehicles 10, one or more vehicles 10 in which the SOC of the energystorage 12 is a relatively high value are selected as the dischargetarget vehicles 10, and one or more vehicles 10 in which the SOC of theenergy storage 12 is a relatively low value are selected as the chargetarget vehicles 10.

In this case, out of the power utilization target vehicles 10, thevehicle 10 having the highest SOC of the energy storage 12 (or anyvehicle 10 in a high SOC state where the SOC is higher than or equal toa predetermined value) is included in the discharge target vehicles 10,and the vehicle 10 having the lowest SOC of the energy storage 12 (orany vehicle 10 in a low SOC state where the SOC is lower than or equalto a predetermined value) is included in the charge target vehicles 10.Also, the discharge target vehicles 10 and the charge target vehicles 10are selected so that the number of charge target vehicles 10 is greaterthan the number of discharge target vehicles 10.

It is to be noted that some of the charge target vehicles 10 and thedischarge target vehicles 10 may not be selected from the powerutilization target vehicles 10. In other words, the total number ofdischarge target vehicles 10 and charge target vehicles 10 may besmaller than the total of power utilization target vehicles 10.

Subsequently, in STEP 7, the controller 3 of the power transmissionmanagement apparatus 1 transmits to each discharge target vehicle 10notification data indicating that the discharge target vehicle 10 isselected as a discharge target vehicle, and transmits to each chargetarget vehicle 10 notification data indicating that the charge targetvehicle 10 is selected as a charge target vehicle.

The notification data is received by respective controllers 15 of eachcharge subject vehicle 10 and each charge subject vehicle 10 (STEP 23,33).

Subsequently, in STEP 8, the controller 3 of the power transmissionmanagement apparatus 1 predicts a degree of variation in SOC achieved bythe SOC variation reduction processing by a simulation.

Specifically, the controller 3 uses variable parameters such as anexecution time length of the SOC variation reduction processing, anamount of discharge (in other words, a discharge current value) per unittime of the energy storage 12 of each discharge target vehicle 10, andan amount of charge (in other words, a charge current value) per unittime of the energy storage 12 of each charge target vehicle 10, andtemporarily sets the value of each variable parameter in a predeterminedvariable range.

It is to be noted that the amount of discharge of each discharge targetvehicle 10 and the amount of charge of each charge target vehicle 10 areset so that the total amount (the total for all the discharge targetvehicles 10) of discharge per unit time of the energy storages 12 of thedischarge target vehicles 10 matches the total amount (the total for allthe charge target vehicles 10) of charge per unit time of the energystorages 12 of the charge target vehicles 10.

In addition, the controller 3 simulates the change in the SOC of theenergy storage 12 of each of the discharge target vehicles 10 and thecharge target vehicles 10 under the assumption that SOC variationreduction processing is performed based on the precondition of thesetting values of the variable parameters.

The controller 3 then calculates a SOC variation degree index value forthe entire power utilization target vehicles 10 using the value of SOC(in other words, an estimated value at the time of completion ofexecution of the SOC variation reduction processing) of the energystorage 12 of each of the discharge target vehicles 10 and the chargetarget vehicles 10 obtained by the simulation. The calculationprocessing is performed similarly to STEP 4. Thus, the SOC variationdegree index value is calculated as a predicted value of a degree ofvariation in the SOC after execution of the SOC variation reductionprocessing.

It is to be noted that in the calculation processing of the SOCvariation degree index value in this case, the value obtained in STEP 1is directly used as the value of SOC of the energy storage 12 of avehicle 10 which is not selected as a discharge target vehicle 10 or asa charge target vehicle 10 out of the power utilization target vehicles10.

Subsequently, in STEP 9, the controller 3 of the power transmissionmanagement apparatus 1 determines whether or not the degree of variationin the SOC predicted in STEP 8 is less than the degree of variation inthe SOC calculated in STEP 4. In the determination processing, morespecifically, for instance, it is determined whether or not the SOCvariation degree index value (a predicted value of the degree ofvariation in SOC after execution of the SOC variation reductionprocessing) calculated in STEP 8 is reduced by a predetermined amountfrom the SOC variation degree index value (the variation degree of SOCwhen execution of the SOC variation reduction processing is started)calculated in STEP 4.

When a result of the determination in STEP 9 is negative, the controller3 changes the values of some variable parameters, and performs theprocessing in STEP 8 again, then further performs the determinationprocessing in STEP 9.

It is to be noted that when a result of the determination in STEP 9 doesnot become affirmative even after the processing in STEP 8 is repeatedfor a predetermined number of times, discharge target vehicles 10 andcharge target vehicles 10 may be re-selected, and the processing in andafter STEP 7 may be performed, for instance.

When a result of the determination in STEP 9 becomes affirmative, thecontroller 3 of the power transmission management apparatus 1 thenperforms the processing in STEP 10.

In STEP 10, the controller 3 transmits a discharge command to dischargethe energy storage 12 of each discharge target vehicle 10 to thedischarge target vehicle 10, and transmits a charge command to chargethe energy storage 12 of each charge target vehicle 10 to the chargetarget vehicle 10.

In this case, as the data specifying the execution time length of theSOC variation reduction processing, and the amount of discharge per unittime of the energy storage 12 of each discharge target vehicle 10, theabove-mentioned discharge command includes data indicating the settingvalue used in the simulation in STEP 8 immediately before a result ofthe determination in STEP 9 becomes affirmative.

Similarly, as the data specifying the execution time length of the SOCvariation reduction processing, and the amount of charge per unit timeof the energy storage 12 of each charge target vehicle 10, theabove-mentioned charge command includes data indicating the settingvalue used in the simulation in STEP 8 immediately before a result ofthe determination in STEP 9 becomes affirmative.

The discharge command transmitted by the controller 3 of the powertransmission management apparatus 1 in STEP 10 is received by thecontroller 15 of each discharge target vehicle 10 (STEP 24), and thecharge command is received by the controller 15 of each charge targetvehicle 10 (STEP 34).

After receiving the discharge command, the controller 15 of thedischarge target vehicle 10 performs discharge control of the energystorage 12 in accordance with the discharge command (STEP 25). In thiscase, in a period with the execution time length of the SOC variationreduction processing specified by the discharge command, the controller15 controls the AC/DC converter 14 so that the energy storage 12 of thedischarge target vehicle 10 is discharged by a specified amount ofdischarge.

After receiving the charge command, the controller 15 of the chargetarget vehicle 10 performs charge control of the energy storage 12 inaccordance with the charge command (STEP 35). In this case, in a periodwith the execution time length of the SOC variation reduction processingspecified by the charge command, the controller 15 controls the AC/DCconverter 14 so that the energy storage 12 of the charge target vehicle10 is charged by a specified amount of charge.

As described above, the discharge control of the energy storage 12 ofeach discharge target vehicle 10 and the charge control of the energystorage 12 of each charge target vehicle 10 are performed, and thus thedischarge power outputted by the energy storage 12 of each dischargetarget vehicle 10 is transmitted from the discharge target vehicle 10 tothe power transmission management apparatus 1 via the external chargingapparatus 5. The total amount of the discharge power received from theenergy storage 12 of each discharge target vehicle 10 by the powertransmission management apparatus 1 is distributed and supplied to theenergy storage 12 of each charge target vehicle 10 from the powertransmission management apparatus 1.

Consequently, the SOC of the energy storage 12 of each discharge targetvehicle 10 decreases, and the SOC of the energy storage 12 of eachcharge target vehicle 10 increases.

In this case, in this embodiment, charge target vehicles 10 anddischarge target vehicles 10 are selected so that the number of chargetarget vehicles 10 is greater than the number of discharge targetvehicles 10. For this reason, the energy storage 12 of each chargetarget vehicle 10 can be charged in a state where the amount of chargeper unit time (so-called charge rate) is low (in short, at a low rate).

Here, in general, when the energy storage 12 is charged at a high rate(in a state where the amount of charge per unit time is high),deterioration is likely to accelerate. However, in this embodiment, theenergy storage 12 of each charge target vehicle 10 can be charged at alow rate. For this reason, acceleration of deterioration of the energystorage 12 can be suppressed as much as possible.

When completing the discharge control of each energy storage 12, next,in STEP 26, the controller 15 of the discharge target vehicle 10transmits discharge result information to the power transmissionmanagement apparatus 1. The discharge result information indicates, forinstance, the total amount of discharge (or the amount of decrease inthe SOC of the energy storage 12) of the energy storage 12 of eachdischarge target vehicle 10 in the SOC variation reduction processingthis time.

Also, when completing the charge control of each energy storage 12,next, in STEP 36, the controller 15 of the charge target vehicle 10transmits charge result information to the power transmission managementapparatus 1. The charge result information indicates, for instance, thetotal amount of charge (or the amount of increase in the SOC of theenergy storage 12) of the energy storage 12 of each charge targetvehicle 10 in the SOC variation reduction processing this time.

The discharge result information and the charge result information arereceived by the controller 3 of the power transmission managementapparatus 1 (STEP 11).

In STEP 12, the controller 3 of the power transmission managementapparatus 1 updates the incentive information recorded in the recorder 3a corresponding to each discharge target vehicle 10 based on thedischarge result information received for each discharge target vehicle10, and updates the incentive information recorded in the recorder 3 acorresponding to each charge target vehicle 10 based on the chargeresult information received for each charge target vehicle 10.

Specifically, the cumulative incentive value for the user of eachdischarge target vehicle 10 is increased by an amount proportional tothe total amount of discharge indicated by the discharge resultinformation. Also, the cumulative incentive value for the user of eachcharge target vehicle 10 is decreased by an amount proportional to thetotal amount of charge indicated by the charge result information. It isto be noted that the cumulative incentive value for the user of a powerutilization target vehicle 10 not selected as a discharge target vehicle10 or a charge target vehicle 10 is maintained at the current valuewithout being increased or decreased.

Here, an increase (in other words, incentive granted per unit dischargeamount) of the incentive value per unit discharge amount of the energystorage 12 of each discharge target vehicle 10 and a decrease (in otherwords, payment cost imposed per unit charge amount) in the incentivevalue per unit charge amount of the energy storage 12 of each chargetarget vehicle 10 in the SOC variation reduction processing are set inadvance. As an example, an increase in the incentive value per unitdischarge amount and a decrease (bearing of cost) in the incentive valueper unit charge amount are set to the same value, for instance.

In this case, as a consequence, an incentive is given and receivedbetween the user of the discharge target vehicle 10 and the user of thecharge target vehicle 10. Therefore, a business operator of the powertransmission management apparatus 1 has substantially no bearing of costfor the SOC variation reduction processing.

After the processing in STEP 12, in STEP 13, the controller 3 of thepower transmission management apparatus 1 transmits incentiveinformation indicating an incentive value after the update to each ofthe discharge target vehicles 10 and the charge target vehicles 10.

The incentive information is received, stored and held by the controller15 of each of the discharge target vehicles 10 and the charge targetvehicles 10 (STEP 26, 36).

The user of the vehicle 10 is informed of the incentive information byvisual display with a display unit or by voice at the time of start ofnext operation of each of the discharge target vehicles 10 and thecharge target vehicles 10.

It is to be noted that the incentive information may be transmitted fromthe power transmission management apparatus 1 addressed to a terminalsuch as a smartphone owned by the user of each of the discharge targetvehicles 10 and the charge target vehicles 10.

After transmitting the incentive information, the controller 3 of thepower transmission management apparatus 1 performs the processing in andafter STEP 4 again. In the processing (processing of calculating a SOCvariation degree index value) in STEP 4 in this case, an estimated valueafter discharge by the discharge control is used as the value of SOC ofthe energy storage 12 of each discharge target vehicle 10, and anestimated value after charge by the charge control is used as the valueof SOC of the energy storage 12 of each charge target vehicle 10.

Here, a result of the determination in STEP 5 subsequent to STEP 4basically indicates negative due to the discharge control of the energystorage 12 of each discharge target vehicle 10 and the charge control ofthe energy storage 12 of each charge target vehicle 10. Thus, the SOCvariation reduction processing is completed.

However, depending on a combination of discharge target vehicles 10 andcharge target vehicles 10 out of the power utilization target vehicles10 or on the setting values of the variable parameters used by thedischarge control and the charge control, reduction in the degree ofvariation in the SOC is insufficient, and eventually, a result of thedetermination in STEP 5 may be affirmative. In this case, the processingin and after STEP6 is performed again.

In this embodiment, the SOC variation reduction processing is performedas described above.

After performing the SOC variation reduction processing, the controller3 of the power transmission management apparatus 1 performs theinstantaneous reserved power transmission processing or the frequencyadjustment processing in cooperation with the controller 15 of each ofthe power utilization target vehicles 10 in a predetermined time period.It is to be noted that the processing performed by the controller 15 ofeach vehicle 10 out of the instantaneous reserved power transmissionprocessing or the frequency adjustment processing corresponds to thefirst control processing in the present disclosure.

In this case, in a time period in which the instantaneous reserved powertransmission processing is performed, for instance, out of the powerutilization target vehicles 10, a vehicle 10, in which the SOC of theenergy storage 12 is higher than or equal to a predetermined lower limitthreshold value (for instance, 10%), is selected as a vehicle thatserves as a power supply source. It is to be noted that the lower limitthreshold value corresponds to the first threshold value in the presentdisclosure.

Then power is supplied from the energy storage 12 of each of selectedvehicles 10 to the power transmission management apparatus 1 via theexternal charging apparatus 5, and the total amount of power istransmitted from the power transmission management apparatus 1 to thepower system 30.

In this case, discharge of the energy storage 12 of each selectedvehicle 10 is performed in a range in which the SOC of the energystorage 12 is maintained to be higher than or equal to the predeterminedlower limit threshold value.

Also, in a time period in which the frequency adjustment processing isperformed, for instance, out of the power utilization target vehicles10, a vehicle 10, in which the SOC of the energy storage 12 is lowerthan or equal to a predetermined upper limit threshold value (forinstance, 90%) and higher than or equal to the predetermined lower limitthreshold value, is selected as a vehicle that transmits and receivespower. It is to be noted that the upper limit threshold valuecorresponds to the second threshold value in the present disclosure.

Then, supplying discharge power of the energy storage 12 of eachselected vehicle 10 to the power system 30 through the powertransmission management apparatus 1, and supplying charge power of theenergy storage 12 of each selected vehicle 10 to the energy storage 12from the power system 30 through the power transmission managementapparatus 1 are alternately repeated.

In this case, when power is transmitted from the power transmissionmanagement apparatus 1 to the power system 30, the total amount ofdischarge power supplied from the energy storage 12 of each selectedvehicle 10 is supplied to the power transmission management apparatus 1.Also, when power is transmitted from the power system 30 to the powertransmission management apparatus 1, the total amount of power receivedfrom the power system 30 by the power transmission management apparatus1 is distributed and supplied to the energy storage 12 of each selectedvehicle 10, and the energy storage 12 is charged.

Next, in a time period after the instantaneous reserved powertransmission processing or the frequency adjustment processing iscompleted, the controller 3 of the power transmission managementapparatus 1 performs processing for charging the energy storage 12 ofeach of the power utilization target vehicles 10 in cooperation with thecontroller 15 of each of the power utilization target vehicles 10.

In this case, from the power transmission management apparatus 1, chargepower of other energy storages 12 is supplied to the power utilizationtarget vehicles 10, in which the SOC (estimated value) of the energystorage 12 falls below a target SOC specified by the charge/dischargerequest, and the energy storage 12 is charged up to the target SOC.

In the charge processing, the power transmission management apparatus 1supplies the power received from the power generation facilities 20 tothe power utilization target vehicles 10 that charge relevant energystorages 12. Also, the charge power is supplied to the energy storages12 of the power utilization target vehicles 10 in a time period which isspecified by the utilization plan related to the power utilizationtarget vehicles 10, and in which charge is completed until the nexttiming of start of use of the power utilization target vehicles 10, andin the time period (for instance, a time period at night), the cost perunit time of the power received from the power generation facilities 20by the power transmission management apparatus 1 is the lowest.

In this embodiment, the payment cost imposed per unit charge amount ofeach energy storage 12 in the charge processing is set to be lower thanthe incentive per unit charge amount of each energy storage 12 in theinstantaneous reserved power transmission processing.

It is to be noted that the charge processing for the energy storage 12of each vehicle 10 other than the power utilization target vehicles 10is performed similarly.

In this embodiment, as described above, the SOC variation reductionprocessing is performed in a time period before power transmission isperformed between the power transmission management apparatus 1 and thepower system 30 by the instantaneous reserved power transmissionprocessing or the frequency adjustment processing. The SOC variationreduction processing reduces the degree of variation in the SOC of theenergy storage 12 of each power utilization target vehicle 10.

For this reason, before the instantaneous reserved power transmissionprocessing or the frequency adjustment processing is performed, the SOCof the energy storage 12 of each power utilization target vehicle 10 islikely to be an intermediate value not too close to 100% or 0%.

Here, when the SOC of an energy storage 12 is 100% or in a high SOCstate near 100%, the energy storage 12 may not be substantially charged,and thus may not be used in the frequency adjustment processing.

Although an energy storage 12 in a high SOC state is usable as an energystorage that performs discharge in the instantaneous reserved powertransmission processing, the discharge amount per unit time has to belower than or equal to a predetermined value in order to protect againstdeterioration or overheating of the energy storage 12. For this reason,the total amount of discharge of the energy storage 12 (energy storage12 in a high SOC state) in a time period in which the instantaneousreserved power transmission processing is performed is likely to be partof possible discharge amount. Eventually, the incentive obtainable bythe user of a vehicle 10 equipped with the energy storage 12 is likelyto be low.

Also, when the SOC of an energy storage 12 is 0% or in a low SOC statenear 0%, the energy storage 12 may not be substantially discharged, andthus may not be used in both the instantaneous reserved powertransmission processing and the frequency adjustment processing.

Therefore, when some energy storages 12 of multiple power utilizationtarget vehicles 10, 10, . . . electrically connected to the powertransmission management apparatus 1 are in a high SOC state or in a lowSOC state, the number of energy storages 12 usable in the instantaneousreserved power transmission processing or the frequency adjustmentprocessing is likely to be small.

Eventually, this tends to create a situation in which it is not possibleto achieve a sufficiently large total amount of power which istransmittable between the power transmission management apparatus 1 andthe power system 30, by utilizing the energy storages 12 of the vehicles10. Also, there is a possibility that the total amount of powertransmittable utilizing the energy storages 12 of the vehicles 10 fallsbelow the amount of power based on a contract. Consequently, the profitobtainable by a business operator of the power transmission managementapparatus 1 or the user of each vehicle 10 is likely to be small.

Furthermore, in general, when the energy storage 12 is left in a highSOC state or a low SOC state for a long time, deterioration of theenergy storage 12 is likely to accelerate.

In this embodiment, as described above, before the instantaneousreserved power transmission processing or the frequency adjustmentprocessing is performed, the SOC of the energy storage 12 of each of thepower utilization target vehicles 10 is likely to be an intermediatevalue due to the SOC variation reduction processing. In other words, theenergy storage 12 of each power utilization target vehicle 10 changesfrom a high SOC state or a low SOC state to an intermediate SOC state,or is maintained in an intermediate SOC state.

An example will be described with reference to FIG. 6. In this example,the number of power utilization target vehicles 10 that undergo the SOCvariation reduction processing is, for instance, four, and therespective SOCs of the energy storages 12 at the start of the SOCvariation reduction processing are 100%, 60%, 40%, and 0%. In this case,the standard deviation as the SOC variation degree index value is 36.0.Hereinafter, the vehicle 10 with a SOC of the energy storage 12 of 100%is denoted by a vehicle 10 a, the vehicle 10 with a SOC of the energystorage 12 of 60% is denoted by a vehicle 10 b, the vehicle 10 with aSOC of the energy storage 12 of 40% is denoted by a vehicle 10 c, andthe vehicle 10 with a SOC of the energy storage 12 of 0% is denoted by avehicle 10 d.

In the SOC variation reduction processing for these vehicles 10 a to 10d, for instance, the vehicle 10 a is selected as a discharge targetvehicle 10 (one vehicle), and the vehicles 10 c, 10 d are each selectedas a charge target vehicle 10 (two vehicles). It is to be noted that inthis example, the vehicle 10 b is not selected as a discharge subjectvehicle 10 or a charge subject vehicle 10.

The energy storage 12 of the vehicle 10 a as a discharge target vehicle10 discharges electricity in an amount equivalent to 50% of the SOC, forinstance, and the vehicles 10 c, 10 d as the charge target vehicles 10are respectively charged with an amount of electricity (⅕ of the totalamount of discharge of the energy storage 12 of the vehicle 10 a)equivalent to 10% of the SOC, and an amount of electricity (⅘ of thetotal amount of discharge of the energy storage 12 of the vehicle 10 a)equivalent to 40% of the SOC. It is to be noted that more particularly,an amount of electricity equivalent to X % of the SOC indicates anamount of electricity of X % of the full charge capacity (=the fullcharge capacity×X/100) of the energy storage 12.

As described above, the respective SOCs of the energy storages 12 of thevehicles 10 a to 10 d at the end of the SOC variation reductionprocessing become 50%, 60%, 50%, and 40% by discharging the energystorage 12 of the vehicle 10 a and the energy storage 12 of each of thevehicles 10 c, 10 d. Therefore, the standard deviation as the SOCvariation degree index value is decreased from 36.0 at the start of theSOC variation reduction processing to 7.1. Also, the SOC of the energystorage 12 of each of the vehicles 10 a to 10 d is in an intermediateSOC state.

In this manner, the degree of variation in the SOC of the energy storage12 of each of the power utilization target vehicles 10 is basicallyreduced by the SOC variation reduction processing. Consequently, the SOCof the energy storage 12 of each of the power utilization targetvehicles 10 is set to an approximately intermediate value.

It is to be noted that in the example illustrated in FIG. 6, as aconsequence of execution of the SOC variation reduction processing, theuser of the vehicle 10 a that discharges the energy storage 12 obtainsan incentive (positive incentive) according to the amount of dischargeof the energy storage 12 (the amount of decrease in SOC), and the usersof the vehicles 10 c, 10 d that charge the respective energy storages 12pay an incentive (negative incentive) according to the amount of chargeof the respective energy storages 12 (the amount of increase in SOC).

As a supplement, in a situation in which the SOCs of the energy storages12 of all power utilization target vehicles 10 are in a high SOC stateor the SOCs of the energy storages 12 of all power utilization targetvehicles 10 are in a low SOC state before the start of execution of theSOC variation reduction processing, it is not possible to change theSOCs of the energy storages 12 of the power utilization target vehicles10 to an intermediate value by the SOC variation reduction processing.However, when the number of power utilization target vehicles 10 issufficiently large, in general, the SOC of the energy storage 12 of eachof the power utilization target vehicles 10 is distributed over variousvalues between a high SOC state and a low SOC state (in general, asituation of partial distribution to only one side of a high SOC stateside and a low SOC state side is unlikely to occur).

Therefore, in most cases, the SOC of the energy storage 12 of each ofthe power utilization target vehicles 10 is set to an approximatelyintermediate value by the SOC variation reduction processing.

In this embodiment, as described above, the SOC of the energy storage 12of each of the power utilization target vehicles 10 is basically set toan approximately intermediate value by the SOC variation reductionprocessing. In this state, the energy storage 12 of each of all thepower utilization target vehicles 10 is utilizable by the instantaneousreserved power transmission processing and the frequency adjustmentprocessing.

Therefore, the power transmission management apparatus 1 can increasethe amount of power transmittable between the power system 30 and thepower transmission management apparatus 1 by the instantaneous reservedpower transmission processing and the frequency adjustment processing.Eventually, the transmission of power can increase the profit obtainedby a business operator of the power transmission management apparatus 1,as well as the incentive to the user of each vehicle 10 utilized by theinstantaneous reserved power transmission processing and the frequencyadjustment processing.

Particularly, in a vehicle 10 (for instance, the vehicle 10 aillustrated in FIG. 6) in which the SOC of the energy storage 12 is in ahigh SOC state before the start of execution of the SOC variationreduction processing, it is possible to discharge much of the originalamount of electricity (the amount of stored energy) of the energystorage 12 by the discharge of the energy storages 12 in the SOCvariation reduction processing, and the discharge of the energy storage12 in instantaneous reserved power transmission processing. Thus, theuser of the vehicle 10 is allowed to obtain much incentive.

Also, a vehicle 10 (for instance, the vehicle 10 d illustrated in FIG.6) in which the SOC of the energy storage 12 is in a low SOC statebefore the start of execution of the SOC variation reduction processingis utilizable in the frequency adjustment processing or utilizable inboth the frequency adjustment processing and the instantaneous reservedpower transmission processing by the charge of the energy storages 12 inthe SOC variation reduction processing.

Therefore, the user of the vehicle 10 is allowed to obtain an incentiveso as to supplement a decrease in the incentive value for the charge ofthe energy storage 12 in the SOC variation reduction processing.

Furthermore, in a vehicle 10 in which the SOC of the energy storage 12is in a high SOC state or in a low SOC state before the start ofexecution of the SOC variation reduction processing, the SOC of theenergy storage 12 is changed to an intermediate SOC by the SOC variationreduction processing. Thus, the energy storage 12 is prohibited frombeing maintained at a high SOC state or a low SOC state for a long time.Consequently, acceleration of deterioration of the energy storage 12 canbe suppressed.

Here, the incentive obtained by the user and the payment cost for eachof the power utilizing target vehicles 10 will be described withreference to FIG. 7 and FIG. 8.

FIG. 7 is a diagram illustrating an embodiment, and FIG. 8 is a diagramillustrating a comparative example. More particularly, FIG. 7 is a bargraph for four vehicles 10 a to 10 d (the vehicles 10 a to 10 d in whichthe original SOCs (initial SOCs) of the energy storages 12 are 100%,60%, 40%, 0%, respectively) exemplified on the upper side of FIG. 6, thebar graph illustrating the incentive obtainable by each user byperforming the SOC variation processing, the instantaneous reservedpower transmission processing, and the frequency adjustment processing,and the payment cost for charge (charge up to a target SOC) of theenergy storage 12 after those processing and operations.

Also, FIG. 8 is a bar graph for the four vehicles 10 a to 10 dillustrating the incentive obtainable by each user by performing theinstantaneous reserved power transmission processing and the frequencyadjustment processing without performing the SOC variation processing,and the payment cost for charge (charge up to a target SOC) of theenergy storage 12 after those operations.

In these embodiment and comparative example, it is assumed that thefinal charge of the energy storage 12 of each of the vehicles 10 a to 10d is performed with a target SOC of 100% of SOC. Also, a maximum valueof total amount of possible discharge of each energy storage 12 in atime period in which the instantaneous reserved power transmissionprocessing is performed is the amount of electricity equivalent to 50%of the SOC.

Also, it is assumed that before the final charge, each energy storage 12is discharged to 10% of the SOC by the instantaneous reserved powertransmission processing. In other words, it is assumed that the amountof charge of each energy storage 12 at the time of the final charge isthe amount of electricity equivalent to 90% of the SOC for each of thevehicles 10 a to 10 d.

Also, it is assumed that the payment cost (incentive bearing) per unitcharge amount of the energy storage 12 of each discharge target vehicle10 in the SOC variation reduction processing is the same (orapproximately the same) as the payment cost at the time of the finalcharge of the energy storage 12.

In the embodiment exemplified in FIG. 7, the user of the vehicle 10 a inwhich the initial SOC of the energy storage 12 is 100% obtains, forinstance, an incentive Aa (incentive according to an amount of dischargeequivalent to 50% of the SOC) for discharge in the SOC variationreduction processing, an incentive Ba (incentive according to an amountof discharge equivalent to 40% of the SOC) for the instantaneousreserved power transmission processing, and an incentive Ca for thefrequency adjustment processing, and bears payment cost Da (costaccording to an amount of charge equivalent to 90% of the SOC) for thefinal charge of the energy storage 12.

Also, the user of the vehicle 10 b in which the initial SOC of theenergy storage 12 is 60% obtains, for instance, the incentive Ba(incentive according to an amount of discharge equivalent to 50% of theSOC) for the instantaneous reserved power transmission processing, andan incentive Cb for the frequency adjustment processing, and bearspayment cost Db (=Da) for the final charge of the energy storage 12. Itis to be noted that as illustrated in FIG. 6, the vehicle 10 b is notselected as a discharge target vehicle 10 or a charge target vehicle 10in the SOC variation reduction processing, and thus the user of thevehicle 10 a does not obtain an incentive or bear payment cost for theSOC variation reduction processing.

Also, the user of the vehicle 10 c in which the initial SOC of theenergy storage 12 is 40% obtains, for instance, an incentive Bc(incentive according to an amount of discharge equivalent to 40% of theSOC) for the instantaneous reserved power transmission processing, andan incentive Cc for the frequency adjustment processing, and bearspayment cost Dc (=Da) for the final charge of the energy storage 12, andpayment cost A′c (payment cost according to an amount of chargeequivalent to 10% of the SOC) for charge in the SOC variation reductionprocessing.

Also, the user of the vehicle 10 d in which the initial SOC of theenergy storage 12 is 0% obtains, for instance, an incentive Bd(incentive according to an amount of discharge equivalent to 30% of theSOC) for the instantaneous reserved power transmission processing, andan incentive Cd for the frequency adjustment processing, and bearscharge cost Dd (=Da) for the final charge of the energy storage 12, andpayment cost A′d (payment cost according to an amount of chargeequivalent to 40% of the SOC) for charge in the SOC variation reductionprocessing.

It is to be noted that in the example of this embodiment, Aa=A′c+A′d.

In contrast, in the comparative example in which the SOC variationreduction processing is not performed, as exemplified in FIG. 8, theuser of the vehicle 10 a in which the initial SOC of the energy storage12 is 100% obtains only the incentive Ba (incentive according to anamount of discharge equivalent to 50% of the SOC) for the instantaneousreserved power transmission processing, and bears payment cost Da(payment cost according to an amount of charge equivalent to 50% of theSOC) for the final charge of the energy storage 12.

It is to be noted that the energy storage 12 of the vehicle 10 a is notutilizable in the frequency adjustment processing, and thus the user ofthe vehicle 10 a is not allowed to obtain the incentive for thefrequency adjustment processing.

Also, the user of the vehicle 10 a in which the initial SOC of theenergy storage 12 is 60% obtains, for instance, an incentive Bb(incentive according to an amount of discharge equivalent to 50% of theSOC) for the instantaneous reserved power transmission processing, andthe incentive Cb for the frequency adjustment processing, and bearscharge cost Db (payment cost according to an amount of charge equivalentto 90% of the SOC) for the final charge of the energy storage 12.

Also, the user of the vehicle 10 c in which the initial SOC of theenergy storage 12 is 40% obtains, for instance, the incentive Bc(incentive according to an amount of discharge equivalent to 30% of theSOC) for the instantaneous reserved power transmission processing, andthe incentive Cc for the frequency adjustment processing, and bearspayment cost Dc (payment cost according to an amount of chargeequivalent to 90% of the SOC) for the final charge of the energy storage12.

Also, the user of the vehicle 10 d in which the initial SOC of theenergy storage 12 is 0% obtains no incentive, and bears payment cost Ddfor the final charge of the energy storage 12.

As seen from the comparison between FIG. 7 and FIG. 8, in the exampleillustrated in FIG. 7, each of the vehicles 10 a to 10 d is utilized inthe instantaneous reserved power transmission processing and thefrequency adjustment processing, and thus the user of each of thevehicles 10 a to 10 d is allowed to obtain an incentive for theinstantaneous reserved power transmission processing and the frequencyadjustment processing.

In contrast, in the comparative example illustrated in FIG. 8, the userof the vehicle 10 a in which the initial SOC of the energy storage 12 is100% is not allowed to obtain an incentive for the frequency adjustmentprocessing, and the user of the vehicle 10 d in which the initial SOC ofthe energy storage 12 is 0% is not allowed to obtain an incentive forthe instantaneous reserved power transmission processing and thefrequency adjustment processing.

In this case, although the vehicle 10 a in the example has an increasedpayment cost Da for charge of the energy storage 12, as compared withthe comparative example, the incentive Aa for discharge in the SOCvariation reduction processing, and the incentive Ca for the frequencyadjustment processing are obtainable. Therefore, the incentives Aa, Caare obtainable so as to supplement an increase in the payment cost Dafor charge of the energy storage 12.

Also, although the user of each of the vehicles 10 c, 10 d in theexample has increased payment costs A′c, A′d for charge in the SOCvariation reduction processing, as compared with the comparativeexample, the incentive for the instantaneous reserved power transmissionprocessing and the frequency adjustment processing is increased. Forthis reason, the payment cost for the user of each of the vehicles 10 c,10 d is reduced, as compared with the comparative example.

In the comparative example illustrated in FIG. 8, vehicles 10, in whichthe power of the energy storage 12 is usable by the power transmissionmanagement apparatus 1 in the instantaneous reserved power transmissionprocessing, are three vehicles 10 a to 10 c, and the total amount ofelectricity which can be discharged from the energy storages 12 of thethree vehicles in a time period of the instantaneous reserved powertransmission processing is the amount of electricity equivalent to 130%of the SOC. Furthermore, in the comparative example, vehicles 10, whichcan repeat charge and discharge of the energy storage 12 in thefrequency adjustment processing, are two vehicles 10 b, 10 c.

In contrast, in the example illustrated in FIG. 7, vehicles 10, in whichthe power of the energy storage 12 is usable by the power transmissionmanagement apparatus 1 in the instantaneous reserved power transmissionprocessing, are four vehicles 10 a to 10 d, and the total amount ofelectricity which can be discharged from the energy storages 12 of thefour vehicles in a time period of the instantaneous reserved powertransmission processing is the amount of electricity equivalent to 170%of the SOC. Therefore, the total amount of electricity which can bedischarged in a time period of the instantaneous reserved powertransmission processing is increased.

Furthermore, in the comparative example, vehicles 10, which can repeatcharge and discharge of the energy storage 12 in the frequencyadjustment processing, are four vehicles 10 a to 10 d, and thus thetotal amount of electricity, which can be given and received between thepower transmission management apparatus 1 and the power system 30utilizing the power of the energy storage 12 in the frequency adjustmentprocessing, is increased, as compared with the comparative example.

According to this embodiment that performs the SOC variation reductionprocessing in this manner, it is possible to increase the amount ofpower which can be transmitted from the power transmission managementapparatus 1 to the power system 30 utilizing the power of the energystorage 12 of each vehicle 10 in the instantaneous reserved supplyoperation, and the amount of electricity which can be given and receivedbetween the power transmission management apparatus 1 and the powersystem 30 utilizing the power of the energy storage 12 of each vehicle10 in the frequency adjustment processing.

Therefore, the profit obtained by a business operator of the powertransmission management apparatus 1 can be increased. Eventually, abusiness operator of the power transmission management apparatus 1 canfurther reduce the unit price of payment cost (payment cost per unitcharge amount) for charge of the energy storage 12 of each of the powerutilizing target vehicles 10, or can further increase the unit price ofincentive (incentive per unit charge amount) for discharge of the energystorage 12 of each of the power utilization target vehicle 10.Consequently, it is possible to further increase the incentive obtainedby the user of each vehicle 10 and to further reduce the payment cost ofthe user.

It is to be noted that in the embodiment described above, in the SOCvariation reduction processing, an increase in the incentive value perunit discharge amount of the energy storage 12 of each discharge targetvehicle 10, and a decrease (bearing of cost) in the incentive value perunit charge amount of the energy storage 12 of each charge targetvehicle 10 are set to the same value. However, for instance, an increasein the incentive value per unit discharge amount may be larger than adecrease in the incentive value per unit charge amount.

Furthermore, an increase in the incentive value per unit dischargeamount of the energy storage 12 of each discharge target vehicle 10 inthe SOC variation reduction processing may be larger than the incentiveper unit charge amount of the energy storage 12 in the instantaneousreserved power transmission processing, for instance.

In this manner, the user of each discharge target vehicle 10 in the SOCvariation reduction processing can obtain more incentive, and thus costadvantage can be improved. Eventually, it is possible to increase thenumber of vehicles 10 that participate in the system (V2G system) inthis embodiment.

Consequently, it is possible to further increase the amount of powertransmittable between the power transmission management apparatus 1 andthe power system 30. Eventually, the profit obtainable by a businessoperator of the power transmission management apparatus 1 can beincreased.

In the embodiment, a case where the transportation unit is the vehicle10 has been described as an example. However, the transportation unit inthe present disclosure may be other than the vehicle 10, for instance, aship, a rail vehicle, or a component transporter vehicle in a productionline.

In the embodiment, a case where the external energy storage is theenergy storage 12 of the vehicle 10 has been described as an example.However, the external energy storage may be a stationary energy storageor the like.

An energy storage system of the present disclosure includes: an energystorage mounted in a transportation unit; a connector that iselectrically connectable to an external power transmission managementapparatus, and that, in a connected state, allows power transmission,via the power transmission management apparatus, between an externalpower system electrically connected to the power transmission managementapparatus, and one or more external energy storages electricallyconnected to the power transmission management apparatus; a powertransmission circuit interposed between the connector and the energystorage; a controller that has a function of controlling the powertransmission circuit. The controller has a function that, in a statewhere the connector is electrically connected to the power transmissionmanagement apparatus, performs A control processing to control the powertransmission circuit in accordance with a command issued from the powertransmission management apparatus so that power transmission isperformed between the energy storage and the power system, and afunction that, when a degree of variation in states of charge of aplurality of energy storages including the energy storage and the one ormore external energy storages is greater than or equal to apredetermined threshold value, performs B control processing to controlthe power transmission circuit before the A control processing isperformed to reduce the degree of variation, in accordance with acommand issued from the power transmission management apparatus so thatpower transmission is performed between the energy storage and the oneor more external energy storages via the power transmission managementapparatus (a first aspect of the disclosure).

It is to be noted that “an any object A (or facility A) is “electricallyconnected” to another object B (or facility B)” in the presentdisclosure indicates a state where power can be transmitted between Aand B at any time (an electric line between A and B is formed). In thiscase, “electrical connection” between A and B is not limited to aconnection state due to contact between conductors, and may be aconnection state where power transmission between A and B is performedwirelessly (via electromagnetic wave energy).

As the external energy storage, for instance, an energy storage mountedin another transportation unit different from the transportation unitsmay be adopted. However, the external energy storage may not be mountedin a transportation unit (the external energy storage may be, forinstance, a stationary energy storage).

According to a first aspect of the disclosure, when a degree ofvariation in the states of charge of multiple energy storages includingan energy storage (hereinafter may be referred to as a mounting energystorage) stationarily mounted in the transportation unit, and theexternal energy storages is greater than or equal to a predeterminedthreshold value, in short, when the degree of variation is large, the Bcontrol processing is performed before the A control processing isperformed.

The degree of variation in the states of charge of the multiple energystorages is reduced by the B control processing. Consequently, thestates of charge of the multiple energy storages are approximately thesame or near values, and in an energy storage (a mounting energy storageor an external energy storage) having an excessively high state ofcharge, the excessively high state can be eliminated as much aspossible, and in an energy storage (a mounting energy storage or anexternal energy storage) having an excessively low state of charge, theexcessively low state can be eliminated as much as possible.

In this manner, the A control processing is performed in a state wherethe degree of variation in the states of charge of the multiple energystorages is reduced. In other words, the power transmission circuit iscontrolled so that power transmission is performed between the mountingenergy storage and the power system.

In this case, since the degree of variation is reduced, all of themultiple energy storages or most of the energy storages can transmitpower between the power system and the energy storages via the powertransmission management apparatus. Eventually, the amount of powertransmitted between the power transmission management apparatus and thepower system can be stably ensured. In addition, charge and discharge ofeach of the energy storages can be controlled in the same manner.

Thus, with the energy storage system according to the first aspect ofthe disclosure, it is possible to stably perform power transmissionbetween the external power system and multiple energy storages includingthe mounting energy storage and the one or more external energy storageswithout using complicated control.

Also, since an excessively high state or an excessively low state of thestates of charge of multiple energy storages can be eliminated as muchas possible by the second control processing, the energy storages areprotected against being left with the states of charge in an excessivelyhigh state or an excessively low state for a long time. Consequently,acceleration of deterioration of each energy storage can be suppressed.

In the first aspect of the disclosure, the command issued from the powertransmission management apparatus to the controller preferably includesone of a discharge command and a charge command, and when the dischargecommand is issued, the controller preferably controls the powertransmission circuit so that the energy storage (mounting energystorage) is discharged, and when the charge command is issued, thecontroller preferably controls the power transmission circuit so thatthe energy storage (mounting energy storage) is charged (a second aspectof the disclosure).

According to this, discharge or charge of the mounting energy storagecan be appropriately performed.

In the second aspect of the disclosure, the discharge command related tothe A control processing is preferably issued to the controller under aprecondition that the state of charge of the energy storage (mountingenergy storage) is higher than or equal to a first predeterminedthreshold value (a third aspect of the disclosure).

According to this, when the state of charge of the mounting energystorage is low (lower than the first threshold value) after the Bcontrol processing is performed, the mounting energy storage is notdischarged in the A control processing, and thus the mounting energystorage is protected against an excessively discharged state.Eventually, acceleration of deterioration of the mounting energy storagecan be suppressed. Also, since the state of charge of the energy storageis ensured (protected against a low state of charge), the mileage of thetransportation unit can be ensured. Therefore, convenience of the userof a transportation unit can be improved.

In the second or third aspect of the disclosure, the charge commandrelated to the A control processing is preferably issued to thecontroller under a precondition that the state of charge of the energystorage (mounting energy storage) is lower than or equal to a secondpredetermined threshold value (a fourth aspect of the disclosure).

According to this, when the state of charge of the mounting energystorage is high (higher than the second threshold value) after the Bcontrol processing is performed, the mounting energy storage is notcharged in the A control processing, and thus the mounting energystorage is protected against an excessively charged state. Eventually,acceleration of deterioration of the mounting energy storage can besuppressed.

It is to be noted that in the present disclosure, the B controlprocessing is performed before the A control processing is performed,thus when the A control processing is performed, a situation, in whichthe state of charge of one of the mounting energy storage and theexternal energy storages is lower than the first threshold value orhigher than the second threshold value, is unlikely to occur. Therefore,the amount of power transmitted between the power system and the energystorages can be sufficiently ensured by the entirety of multiple energystorages including the mounting energy storage.

In the first to fourth aspects of the disclosure, the controllerpreferably performs the B control processing that discharges the energystorage (mounting energy storage), in a state which allows powertransmission from the energy storage (mounting energy storage) to two ormore external energy storages (a fifth aspect of the disclosure).

According to this, the charge rate (charge amount per unit time) of theexternal energy storage that is charged by the B control processing canbe reduced as much as possible. Thus, acceleration of deterioration ofthe external energy storage can be suppressed.

In the first to fifth aspects of the disclosure, the controllerpreferably performs the B control processing that charges the energystorage (mounting energy storage), in a state where a total number ofexternal energy storages that are charged along with the energy storage(mounting energy storage), and the energy storage (mounting energystorage) out of the energy storage (mounting energy storage) and theexternal energy storages is greater than a number of the external energystorages that discharge energy (a sixth aspect of the disclosure).

According to this, the charge rate (charge amount per unit time) of themounting energy storage that is charged by the B control processing canbe reduced as much as possible. Thus, acceleration of deterioration ofthe mounting energy storage can be suppressed.

In the first to sixth aspects of the disclosure, the controller may havea function that, when the energy storage (mounting energy storage) ischarged or discharged by the A control processing, obtains dataindicating an increase in a cumulative incentive value from the powertransmission management apparatus, and further has a function thatinforms of information on change in the incentive value (a seventhaspect of the disclosure).

According to this, when the mounting energy storage is charged ordischarged by the A control processing, the incentive value isincreased. Then, the user is informed of information on change in theincentive value. Thus, the user of the transportation unit can obtain anincentive by charging or discharging the energy storage in the A controlprocessing, and can recognize a change in the incentive value(cumulative incentive value).

In the seventh aspect of the disclosure, the controller preferably has afunction that, when the energy storage (mounting energy storage) ischarged or discharged by the A control processing, obtains dataindicating an increase in a cumulative incentive value from the powertransmission management apparatus, and further has a function thatinforms of information on change in the incentive value (an eighthaspect of the disclosure).

According to this, when the mounting energy storage is discharged by theB control processing, the user of the transportation unit can obtainfurther incentive, and can recognize a change in the incentive value.

In the eighth aspect of the disclosure, the controller may further havea function that, when the energy storage (mounting energy storage) ischarged by the B control processing, obtains data indicating a decreasein the incentive value from the power transmission management apparatus(a ninth aspect of the disclosure).

According to this, when the mounting energy storage is discharged by theB control processing, the incentive value of the user of thetransportation unit is decreased. It is possible to give the decrease tothe user of the external energy storage as an incentive. Thus, abusiness operator of the power transmission management apparatus caneliminate or reduce bearing of cost in the second control processing.

In the eighth or ninth aspect of the disclosure, a configuration may beadopted in which an increase in the incentive value per unit dischargeamount of the energy storage (mounting energy storage) when the energystorage (mounting energy storage) is discharged by the B controlprocessing is greater than an increase in the incentive value per unitdischarge amount of the energy storage (mounting energy storage) whenthe energy storage (mounting energy storage) is discharged by the Acontrol processing (a tenth aspect of the disclosure).

According to this, when the mounting energy storage is discharged by thesecond control processing, the user of the transportation unit canobtain much incentive. Therefore, discharging the mounting energystorage by the second control processing has an advantage in cost.Eventually, the user of each of many transportation units makes anactive effort to electrically connect the energy storage of thetransportation unit to the power transmission management apparatus.Consequently, the profit obtainable by a business operator of the powertransmission management apparatus for power transmission between thepower system and the power transmission management apparatus is furtherincreased, and the incentive obtainable by the user of eachtransportation unit is further increased.

Also, the transportation unit in the present disclosure includes theenergy storage system according to the first to tenth aspects of thedisclosure (11th aspect of the disclosure).

According to this, the same effect as that of the first to tenth aspectsof the disclosure can be achieved.

A method of controlling an energy storage system in the presentdisclosure including: an energy storage mounted in a transportationunit, a connector that is electrically connectable to an external powertransmission management apparatus, and that, in a connected state,allows power transmission, via the power transmission managementapparatus, between an external power system electrically connected tothe power transmission management apparatus, and one or more externalenergy storages electrically connected to the power transmissionmanagement apparatus, and a power transmission circuit interposedbetween the connector and the energy storage, the method including: in astate where the connector is electrically connected to the powertransmission management apparatus, controlling the power transmissioncircuit to perform power transmission between the energy storage and thepower system, and when a degree of variation in states of charge of aplurality of energy storages including the energy storage and the one ormore external energy storages is greater than or equal to apredetermined threshold value, to reduce the degree of variation beforethe controlling the power transmission circuit, controlling the powertransmission circuit to perform power transmission between the energystorage and the one or more external energy storages via the powertransmission management apparatus (12th aspect of the disclosure).

According to this, the same effect as that of the first aspect of thedisclosure can be achieved.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. An energy storage system comprising: an energystorage mounted in a transportation unit; a connector that iselectrically connectable to an external power transmission managementapparatus, and that, in a connected state, allows power transmission,via the power transmission management apparatus, between an externalpower system electrically connected to the power transmission managementapparatus, and one or more external energy storages electricallyconnected to the power transmission management apparatus; a powertransmission circuit interposed between the connector and the energystorage; a controller that has a function of controlling the powertransmission circuit, wherein the controller has a function that, in astate where the connector is electrically connected to the powertransmission management apparatus, performs A control processing tocontrol the power transmission circuit in accordance with a commandissued from the power transmission management apparatus so that powertransmission is performed between the energy storage and the powersystem, and a function that, when a degree of variation in states ofcharge of a plurality of energy storages including the energy storageand the one or more external energy storages is greater than or equal toa predetermined threshold value, performs B control processing tocontrol the power transmission circuit before the A control processingis performed to reduce the degree of variation, in accordance with acommand issued from the power transmission management apparatus so thatpower transmission is performed between the energy storage and the oneor more external energy storages via the power transmission managementapparatus.
 2. The energy storage system according to claim 1, whereinthe command issued from the power transmission management apparatus tothe controller includes one of a discharge command and a charge command,and when the discharge command is issued, the controller controls thepower transmission circuit so that the energy storage is discharged, andwhen the charge command is issued, the controller controls the powertransmission circuit so that the energy storage is charged.
 3. Theenergy storage system according to claim 2, wherein the dischargecommand related to the A control processing is issued to the controllerunder a precondition that the state of charge of the energy storage ishigher than or equal to a first predetermined threshold value.
 4. Theenergy storage system according to claim 2, wherein the charge commandrelated to the A control processing is issued to the controller under aprecondition that the state of charge of the energy storage is lowerthan or equal to a second predetermined threshold value.
 5. The energystorage system according to claim 1, wherein the controller performs theB control processing that discharges the energy storage, in a statewhich allows power transmission from the energy storage to two or moreexternal energy storages.
 6. The energy storage system according toclaim 1, wherein the controller performs the B control processing thatcharges the energy storage, in a state where a total number of externalenergy storages that are charged along with the energy storage, and theenergy storage out of the energy storage and the external energystorages is greater than a number of the external energy storages thatdischarge energy.
 7. The energy storage system according to claim 1,wherein the controller has a function that, when the energy storage ischarged or discharged by the A control processing, obtains dataindicating an increase in a cumulative incentive value from the powertransmission management apparatus, and further has a function thatinforms of information on change in the incentive value.
 8. The energystorage system according to claim 7, wherein the controller further hasa function that, when the energy storage is discharged by the B controlprocessing, obtains data indicating an increase in the incentive valuefrom the power transmission management apparatus.
 9. The energy storagesystem according to claim 8, wherein the controller further has afunction that, when the energy storage is charged by the B controlprocessing, obtains data indicating a decrease in the incentive valuefrom the power transmission management apparatus.
 10. The energy storagesystem according to claim 8, wherein an increase in the incentive valueper unit discharge amount of the energy storage when the energy storageis discharged by the B control processing is greater than an increase inthe incentive value per unit discharge amount of the energy storage whenthe energy storage is discharged by the A control processing.
 11. Atransportation unit including the energy storage system according toclaim
 1. 12. A method of controlling an energy storage system including:an energy storage mounted in a transportation unit, a connector that iselectrically connectable to an external power transmission managementapparatus, and that, in a connected state, allows power transmission,via the power transmission management apparatus, between an externalpower system electrically connected to the power transmission managementapparatus, and one or more external energy storages electricallyconnected to the power transmission management apparatus, and a powertransmission circuit interposed between the connector and the energystorage, the method comprising: in a state where the connector iselectrically connected to the power transmission management apparatus,controlling the power transmission circuit to perform power transmissionbetween the energy storage and the power system, and when a degree ofvariation in states of charge of a plurality of energy storagesincluding the energy storage and the one or more external energystorages is greater than or equal to a predetermined threshold value, toreduce the degree of variation before the controlling the powertransmission circuit, controlling the power transmission circuit toperform power transmission between the energy storage and the one ormore external energy storages via the power transmission managementapparatus.
 13. An energy storage system comprising: an energy storageprovided in a transportation unit; a connector electrically connectableto an external power transmission management apparatus that iselectrically connectable to an external power system and one or moreexternal energy storages; a power transmission circuit interposedbetween the connector and the energy storage; and a processor configuredto control the power transmission circuit in accordance with an outputfrom the external power transmission management apparatus to performpower transmission between the energy storage and the external powersystem, and control the power transmission circuit in accordance with anoutput from the external power transmission management apparatus, if adegree of variation in charging states in the energy storage and the oneor more external energy storages is greater than or equal to a thresholdvalue, to perform power transmission between the energy storage and theone or more external energy storages via the external power transmissionmanagement apparatus to reduce the degree of variation before performingthe power transmission between the energy storage and the external powersystem.
 14. The energy storage system according to claim 13, wherein theoutput from the power transmission management apparatus to the processorincludes one of a discharge command and a charge command, and if thedischarge command is issued, the processor controls the powertransmission circuit so that the energy storage is discharged, and ifthe charge command is issued, the processor controls the powertransmission circuit so that the energy storage is charged.
 15. Theenergy storage system according to claim 14, wherein the dischargecommand related to the power transmission between the energy storage andthe external power system is issued to the processor under aprecondition that the state of charge of the energy storage is higherthan or equal to a first threshold value.
 16. The energy storage systemaccording to claim 14, wherein the charge command related to the powertransmission between the energy storage and the external power system isissued to the processor under a precondition that the state of charge ofthe energy storage is lower than or equal to a second threshold value.17. The energy storage system according to claim 13, wherein theprocessor is configured to perform the power transmission between theenergy storage and the one or more external energy storages to dischargethe energy storage, in a state where power transmission is to beperformed from the energy storage to two or more external energystorages.
 18. The energy storage system according to claim 13, whereinthe processor is configured to perform the power transmission betweenthe energy storage and the one or more external energy storages tocharge the energy storage, in a state where a total number of externalenergy storages that are charged along with the energy storage, and theenergy storage out of the energy storage and the external energystorages is greater than a number of the external energy storages thatdischarge energy.
 19. The energy storage system according to claim 13,wherein the processor is configured to, if the energy storage is chargedor discharged by the power transmission between the energy storage andthe external power system, obtain data indicating an increase in acumulative incentive value from the power transmission managementapparatus, and inform of information on change in the incentive value.20. The energy storage system according to claim 19, wherein theprocessor is further configured to, if the energy storage is dischargedby the power transmission between the energy storage and the one or moreexternal energy storages, obtain data indicating an increase in theincentive value from the power transmission management apparatus. 21.The energy storage system according to claim 20, wherein the processoris further configured to, if the energy storage is charged by the powertransmission between the energy storage and the one or more externalenergy storages, obtain data indicating a decrease in the incentivevalue from the power transmission management apparatus.
 22. The energystorage system according to claim 20, wherein an increase in theincentive value per unit discharge amount of the energy storage if theenergy storage is discharged by the power transmission between theenergy storage and the one or more external energy storages is greaterthan an increase in the incentive value per unit discharge amount of theenergy storage when the energy storage is discharged by the powertransmission between the energy storage and the external power system.23. A transportation unit including the energy storage system accordingto claim
 13. 24. A method of controlling an energy storage system, themethod comprising: controlling a power transmission circuit to performpower transmission between an energy storage and an external powersystem, the energy storage system including the energy storage providedin a transportation unit, the connector electrically connectable to theexternal power transmission management apparatus that is electricallyconnectable to the external power system and one or more external energystorages, and the power transmission circuit interposed between theconnector and the energy storage; and if a degree of variation in statesof charge of the energy storage and the one or more external energystorages is greater than or equal to a threshold value, controlling thepower transmission circuit to perform power transmission between theenergy storage and the one or more external energy storages via thepower transmission management apparatus to reduce the degree ofvariation before performing the power transmission between the energystorage and the external power system.